The present invention relates to optical devices and is particularly applicable but not limited to devices and methods for flexible and fast control of such optical devices.
The telecommunications revolution of the past few years has seen the increasing migration of telecommunications traffic from conventional copper wire networks to optical networks. This migration has led to an increased demand for not only optical components but also for better means of controlling them.
Conventional optical devices are currently controlled by means of a digital interface. An RS-232 interface, with appropriate corresponding circuitry, is usually interface with an optical device. A control word is sent from a personal computer or a dedicated microcontroller to the RS-232 interface to control the optical device using generally accepted communications protocols.
This control scheme can be seen schematically in FIG. 1. The optical device 2 interfaces with a microcontroller 4 for controlling the optical device. The microcontroller 4 is usually equipped with a suitable digital interface such as an RS-232 or a serial LVTTL for communicating with a second microcontroller 6. The second microcontroller 6 sets the parameters for the optical device based on external data or stimuli.
One drawback of this current control scheme is the use of a computer-based interface such as the RS-232 interface. While such interfaces are useful for their programability, they suffer from the limitations of the digital nature of the interface. The speeds at which the data can be sent to the optical device is limited by the speed of the interface. Furthermore, such a digital interface necessarily requires extra processing that can add further delays to the time delay between the control signal being sent and the reaction of the device. Also, the use of a communications protocol to communicate to the device can be quite cumbersome.
Another possible drawback to the digital interface is its reliability. The use of digital processing requires the presence of fragile digital processing equipment between the optical device and the end user. If such digital equipment is used in an installation, such equipment is subject to breakdown, interruption, and damage from extraneous factors as weather, weather effect such as lightning storms, and natural catastrophes such as earthquakes and fires. These occurrences can severely affect digital equipment, thereby interrupting any optical communications links carried by the optical device controlled by the digital equipment.
An economic drawback of the current control schemes for optical devices is the presence of the RS-232 interface. This interface requires a costly computer or micro-controller positioned between the optical device and any control signals. Analog control signals need to be digitized and approximated while digital control signals need to be translated into a format acceptable to the RS-232 interface.
It should be clear that an alternative to the current optical device interfaces is needed. Such a solution should allow direct control of the optical device and such direct control should allow for shorter periods between the control signal being received and a corresponding change in the optical device output. Such a solution should also be less fragile than the current digital interfaces.
The present invention relates to methods and devices for controlling an optical device. In one embodiment, the optical device is directly controlled by an outside analog electrical signal. Depending on the voltage or current level of the electrical signal, the output of the optical device is changed accordingly. An operational amplifier may be used to amplify the analog electrical signal prior to the signal being received by the circuitry of the optical device. For maximum flexibility in control, a switch can be coupled to the operational amplifier so that either analog or digital control signals can be used.
In a first aspect, the present invention provides a method of directly controlling an optical device with a controllable output, the method comprising:
a) receiving an electrical signal; and
b) changing an output level of the optical device based on a characteristic of said electrical signal.
In a second aspect, the present invention provides an optical device module comprising:
an optical device;
receiving means for receiving an electrical signal for controlling said optical device; and
control means for controlling an output level of said optical device based on a characteristic of said electrical signal wherein said receiving means is coupled to said control means and said control means is coupled to said optical device.
In a third aspect, the present invention provides an optical device module comprising:
an optical device;
receiving means for receiving a signal for controlling said optical device;
control means for controlling an output level of said optical device based on said signal; and
switch means for switching and choosing a control signal from at least two control signals, a chosen control signal being passed on to said receiving means, wherein said receiving means is coupled to said control means and said control means is coupled to said optical device, said switch means being coupled to said receiving means.
In a fourth aspect, the present invention provides a method of controlling an optical device with a controllable output, the method comprising:
a) receiving at least two control signals for controlling said optical device, at least one of said at least two control signals being an analog electrical signal;
b) selecting one of said at least two control signals;
c) in the event a selected control signal is an analog electrical signal, changing an output level of the optical device based on a characteristic of said electrical signal.